a. Field of the Invention
This invention is related to electrical safety switches.
b. Related Art
Switches commonly require one or more auxiliary contacts for functions such as annunciation or motor controller operation. The auxiliary contacts are typically provided by way of an additional or auxiliary switch, mounted in the same housing as the main switch. When used for annunciation, the contacts of the auxiliary switch are typically disposed so as to close after the main switch closes and to open before the main switch opens. This ensures a positive operation of other circuit protection devices correctly sequenced with the main switch contact operation. An example of a prior art spring operated electrical safety switch is shown in FIG. 1. The switch of FIG. 1 is provided with movable contact carriers 102, each of which holds an electrically conductive contact 104. The contact carriers 102 are mounted on a spring loaded bail 106, which is pivotally mounted to the switch housing 108 by way of a pin 107 and a drive shaft 116. Multiple pairs of stationary electrical contacts 110, 112 are also mounted within the switch housing 108 so as to receive the movable contacts 104 when the switch is "on". One electrical contact 110 in each pair is connected to a line voltage while the other electrical contact 112 in each pair is connected to a load. A handle 114 is connected to the bail 106 by way of the drive shaft 116 and an operating cam 118. A spring 120 is also mounted to the switch housing 108 and coupled to the bail 106 so as to bias the bail 106 in a position such that each of the movable contacts 104 will be brought into mechanical and electrical connection with a corresponding pair of the stationary contacts 110, 112. A rod 122, centered within the spring transfers the force of the spring to the cam 118. By pulling the handle 114, the user loads the spring 120 which, in turn, pivots the bail 106 into an "over center" position away from the stationary contacts, thus leaving the switch in an "off" or "open" position.
When the handle 114 is lifted in an upward direction by the user, the cam 118 pivots the bail 106. Once pivoted beyond the center position, in the direction of the stationary contacts 110, 112, the bail 106 slips from the handle 114 as the spring 108 pushes the bail 106 into place. When the bail is in place in it's spring biased position, the movable contacts 104 each make mechanical and electrical connection between a corresponding pair of stationary contacts 110, 112, thus placing the switch into a "on" or "closed" position.
An enlarged view of the bail 106, the pin 107, a movable contact carrier 102, a movable contact 104 and a pair of stationary contacts 110, 112 is illustrated in FIG. 2. As is known in the art, an auxiliary switch 124 may be mounted in a position within the housing such that the top end (carries portion) 106a of the bail 106 (the section on which the contact carriers 102 are mounted) will cause the auxiliary switch 124 to be "closed" just after the bail 106 and contacts 104 are pulled into a "closed" position by the spring 108. The switch 124 is provided with an actuator 126 on a side facing the bail and wiring contacts on the opposite side.
While the above-described configuration provides a suitable auxiliary contact in many situations, one problem with such switches is that the configuration does not readily lend itself to the use of larger current rated versions of conventional top wired/bottom actuated switches since the space within the cabinet below the bail bar is highly limited. Instead, the prior art switches often resort to smaller/lower current rated switches, mounting external to the mechanism and/or non-conventional switch configurations or wiring arrangements.
For example, mounting a conventional top-wired/bottom actuated micro-switch in the position shown in FIG. 1 would place the wire contact screw at the bottom and leave it relatively inaccessible. Further, while an actuator could be devised, a different one would typically be required for each different bail diameter.